IsHTMLDDA is specified in INTERPRETING.md to return null on [[Call]]
when called with no arguments or with single argument "". Return null
causes the iterator protocol to throw.
Also see star-iterable-return-emulates-undefined-throws-when-called.js
Modify $262.uncallableAndIsHTMLDDA() to an optional $262.IsHTMLDDA (whose use must be guarded by a feature of the same name), and narrowly/correctly prescribe its requirements consistent with `document.all`'s behavior in HTML.
Shu-yu Guo
Alexey Shvayka
Jeff Walden